This invention relates to scratch resistant surfaces, and more particularly to a scratch resistant display such as a computer touch screen panel.
Surface scratches affect product appearance and function in detrimental ways. This is especially true in the optics and display industry where the surface is coated with a layer or layers intended to provide a specific function such as a filter or dielectric coating. In particular, computer touch screen panels are especially vulnerable. Touch screens have become more and more popular as a input device for computers. A touch is sensed by a touch screen when a finger or a stylus comes into contact with the outermost surface of the touch screen panel. The contact is translated into x and y coordinates of the finger or stylus on the panel. Since the data entry is based on contact, touch screen panels are inherently susceptible to scratches.
A scratch is made by a plastic deformation on a surface. The force that produces a scratch can be divided into two components: a component that is perpendicular to the surface and another component parallel to the surface. The component perpendicular to the surface produces a plastic deformation on the surface and the component parallel to the surface extends the damage by plowing material out of the way. The damage due to the perpendicular component is dependent upon on the friction of the contact surfaces. The higher the friction coefficient, the larger the perpendicular component and thus the more damage which results.
Two of the most widely employed approaches for providing scratch resistance to a surface are the introduction of lubricants and solid/hard protective coatings applied to the outer most layer of the touch screen. The introduction of a lubricant reduces the energy dissipation along the surface attributable to the vertical component which would otherwise cause damage to the surface. Solid/hard coatings are intended to avoid the initial plastic deformation in the first place. Neither lubricants nor solid/hard protective coatings, however, provide sufficient scratch resistance to touch screen panels.
Non-homeotropic organosilanes have long been used as coupling agents which provide a stable bond between dissimilar surfaces. It is an important characteristic of coupling agents that they form a chemical bond to surface materials. Most of the anti-scratch surface treatments involve providing hard coatings although some use organosilanes to improve lubricity of glass surfaces.
Several other families of organosilanes have been tested. These include alkylsiloxanes, alkylaminosiloxanes, perfluoroalkylsiloxanes. None of these organosilanes, however, have been found to improve scratch resistance to the extent required for touch screen panels.
Touch screen panels can be found everywhere from ATM""s to casinos to bar room video games. These environments are extremely harsh and susceptible to scratching from coins, bottles and glasses as well as being exposed to harsh outdoor elements where they are subject to airborne debris and even vandalism. Depending on the severity of the scratch, the function of the display may be greatly affected.
It is therefore an object of this invention to provide a display which is scratch resistant.
It is a further object of this invention to provide such a scratch resistant display which is durable and long lasting.
It is a further object of this invention to provide a scratch resistant surface which is simpler to produce and more durable than current hard coatings.
It is a further object of this invention to provide such a scratch resistant surface which can be applied to most any coated surface.
The invention results from the realization that a truly durable and long lasting scratch resistant display can be obtained by applying a homeotropic organosilane to the outer most surface of the display to reduce energy dissipation of an object as the object is dragged transverse to the surface.
This invention features a scratch resistant display comprising a substrate, an active portion on one surface of the substrate including at least a conductive layer, and a homeotropic organosilane layer deposited on the active portion for reducing energy dissipation of an object contacting the display.
In a preferred embodiment the active portion may include a protective layer on the conductive layer. The active portion may include a deformable conductive layer on the conductive layer. The organosilane may include a liquid crystal silane. The substrate may be transparent. The transparent substrate may be glass. The display may be a touch screen panel. The first conductive layer may include a tin oxide. There may be a second conductive layer disposed on the substrate on a surface opposite the active portion. The first and the second conductive layers may be tin oxide.
The invention also features a scratch resistant touch screen panel having an insulative substrate, a conductive layer disposed on one surface of the insulative substrate, a protective layer disposed on the conductive layer, and a homeotropic organosilane layer disposed on the protective layer for reducing energy dissipation of an object contacting the touch screen panel.
The invention also features a scratch resistant touch screen panel having an insulative substrate, an active portion disposed on the substrate, the active portion having at least a first conductive layer disposed adjacent the insulative substrate, a deformable conductive layer adjacent and spaced from the first conductive layer, and a protective layer disposed on the deformable conductive layer. There is a homeotropic organosilane layer disposed on the active portion for reducing energy dissipation of an object contacting the touch screen panel.
The invention also features a method for producing a scratch resistant coated transparent article by combining a transportation medium and a homeotropic organosilane, and applying the combination to a coated transparent article to be protected.
In a preferred embodiment the organosilane may include a liquid crystal silane. The article may be heated, after applying the combination, to a temperature below the disassociation temperature of the combination. The transportation medium may include water. The transportation medium may include alcohol.